Using a lever to move a rock reduces the force a person must exert. What does it do to the work the person must do?
a. it reduces the work also c. the work increases
b. the work stays the same d. none of the above
B
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Kepler's Laws: Two moons orbit a planet in circular orbits. Moon A has orbital radius R, and moon B has orbital radius 4R. Moon A takes 20 days to complete one orbit. How long does it take moon B to complete an orbit?
A. 20 days B. 80 days C. 160 days D. 320 days E. 5 days
When a massive star begins to run out of hydrogen to fuse, its outer layers of gas ________.
A. expand and cool B. contract and heat C. contract and cool D. expand and heat
A 1.53-kg piece of iron is hung by a vertical ideal spring. When perturbed slightly, the system is moves up and down in simple harmonic oscillations with a frequency of 1.95 Hz and an amplitude of 7.50 cm
If we choose the total potential energy (elastic and gravitational) to be zero at the equilibrium position of the hanging iron, what is the total mechanical energy of the system? A) 0.633 J B) 0.955 J C) 0.646 J D) 0.000 J E) 0.844 J
How can precision of a measuring instrument be increased?